Wide area communication networks, which contain both wired and wireless networks, are an attractive method of data transmission over long distances for remote sensor data acquisition, processing and control applications. When used in such communication systems, wireless networks have obvious advantages of eliminating the need for costly wired network infrastructures and being more convenient. Wireless networks also enable data transmission from harsh environments and locations, which may be difficult or impossible to access by wired networks and offer much greater freedom in terms of mobility and area coverage.
For all their advantages, however, wide area communication networks with wireless network segments typically have a few major limitations. One typical limitation of wireless networks is their limited and highly variable link bandwidth. Other limitations of wireless networks include their susceptibility to bandwidth losses due to various kinds of interference, their reduction in throughput performance due to attenuation of radio signals with distance and performance degradation due to attenuating objects in the signal path. Additionally, the user of the ubiquitous Transmission Control Protocol (TCP), which is not optimized for use in wireless networks, is another factor that can reduce the available bandwidth of wireless networks. Wide area communication networks with shared network segments can also have variable link bandwidth depending on the network traffic.
While these limitations may not be of concern for applications with low bandwidth requirements and tolerance to high data latencies, it is often a problem for real-time applications. In many real-time applications, the usefulness of the data decays rapidly with time. Therefore, the latency in the communication network must be managed to avoid stale data. For networks with constrained and variable network bandwidth, the data latency and the required data rate (required throughput) are interrelated. Therefore, neither desired throughput nor latency can be guaranteed.